The present invention relates to an electron beam exposure technique. More specifically, the present invention relates to high-precision electron beam exposure equipment and exposure method.
In electron beam writing equipment, optical adjustment of an electron beam is one of the most important techniques.
In a prior art, axis adjustment of an electron beam lens is performed by measuring the change of position of an electron beam with changing the focus length of the lens (for example, see Micro Electronic Engineering, vol. 21, 1993, pp. 145-148). The method, however, is used only in a point beam and a micro area beam substantially handled as a point beam in which a crossover is larger than an image. In addition, a focal point is changed by varying excitation of one lens.
There are electron beam exposure equipment having a method for projecting a large field electron beam onto a sample and a method for exposing a large field by plural electron beams at the same time. In these methods, there is no guide for the above axis adjustment. In a method for using plural electron beams which can control on/off independently in the large field projection methods, correction using only a specific electron beam is proposed (for example, see Japanese Patent Application Laid-Open No. 10-106931). In such proposition, a method about optical adjustment of a lens is not described.
Further, in a prior art, a method for adjusting an optics system of large field projection is proposed. To permit wide deflection, plural detectors and lens interference are finely adjusted to ultimately change the lens characteristic, thereby realizing low aberration. It is very complex (for example, see Japanese Patent Application Laid-Open No. 10-303095).
As a simplified method, a method for adjusting the position of a crossover (pupil image) is proposed. This method is limited (for example, see Japanese Patent Application Laid-Open No. 10-302696).
In large field projection aiming at higher throughput, an electron optics system using a doublet lens is required. The doublet lens substantially equalizes the sum of the focus lengths of two electromagnetic lenses and the distance between the two electromagnetic lenses to form one image plane by the two electromagnetic lenses. In the above prior art, a simplified optical adjustment method for using the lenses of this method with high precision is not considered.